This invention is a continuation-in-part of the invention described in my application Ser. No. 12/460,790 that was filed as a non-provisional application on Jul. 24, 2009, now U.S. Pat. No. 8,085,621 and is concerned with further improvements in the design of electroacoustic transducers for transmitting or receiving sound in a fluid medium, as described in said co-pending application. Although not limited to the ultrasonic frequency region, this improvement in the performance characteristics of electroacoustic transducers is primarily to be used in the ultrasonic frequency region in a gaseous medium.
The teachings of this invention can be used by one skilled in the art in a wide variety of transducer designs using many different methods of transduction for sound radiation or reception in fluid or gaseous mediums. Transducers using the teachings of this invention can be designed using a wide variety of transduction materials, such as magnetostrictive rods, piezoelectric crystals, and polarized ceramic elements. However, the teachings of this invention can best be used in conjunction with ultrasonic transducers designed with polarized ceramic.
The co-pending application describes an ultrasonic transducer that utilizes an acoustic transmission line to increase the sensitivity of both the transmitting response and the receiving response. The resonant element of the transducer could employ a ceramic disc operating in the radial resonance mode for its transduction means, or it could be a half wavelength resonator utilizing a forward transmission line, a rear transmission line, and a non-resonant ceramic for transduction. The shape of the forward transmission line is designed to generate the desired acoustic radiation pattern at the frequency of resonance, which could be a broad or narrow conical beam or a fan shaped beam.
In operation, the radiating face of the transducer described in the co-pending application must be exposed to the fluid medium in order to efficiently transmit and receive sound pulses with the desired acoustic radiation patterns. Having the face of the transducer exposed is usually not a problem in most echo-ranging applications. However, in certain cases, such as sensors used in the automotive industry, having transducers mounted onto the vehicle visibly is not desirable because it interferes with the look and style of the car. Therefore, in automotive acoustic echo-ranging applications, such as park assist systems, it would be a great advantage to hide the transducers mounted onto the vehicle so that they are not visible. This invention extends the teachings of the co-pending application to allow the ultrasonic transducer to be invisibly mounted onto platforms such as automobiles.